The invention relates to a device for converting energy using fuel cells with a proton-hydrogen electrolyte and an integrated device for hydrogen gas production and, further the invention relates precharacterizing, to a method of producing hydrogen gas (H.sub.2 gas) with a means which is integrated into such a device for converting energy using fuel cells, the H.sub.2 gas being used as a combustion gas for the fuel cells.
Fuel cells can be used for converting hydrogen (H.sub.2) directly into electric current by reacting with oxygen (O.sub.2). The use of such fuel cells thus depends on the availability of H.sub.2 gas. Fuel cells with a proton-conducting electrolyte are therefore supplied with stored H.sub.2. This gaseous fuel can either be adsorbed in metal hydrides at room temperature under pressure (for example 200 bar), at temperatures around -150.degree. C., or be stored in liquid form at -255.degree. C. All three possible types of storage are laborious, expensive, complicated in terms of handling and require the use of heavy, voluminous containers. Furthermore, H.sub.2 is always also potentially hazardous, since it is very reactive and may explode.
As known, for example from EP 206 608, EP 404 712, EP 729 196 or U.S. Pat. No. 4,642,272, H.sub.2 can be produced chemically from hydrocarbons (methane, methanol, benzene etc.). Water vapor is admixed to the fuel at an elevated temperature in catalytic converters, the hydrocarbon molecules being converted into H.sub.2 and carbon monoxide (CO). In a second reaction stage, the CO then reacts, when water vapor is added, to give carbon dioxide (CO.sub.2). This again causes H.sub.2 to be produced. In a third stage, CO and CO.sub.2 must be carefully separated from the H.sub.2, in order to avoid "poisoning" the platinum electrodes of the fuel cell. This way of producing H.sub.2 is laborious, cost-intensive and efficiency-reducing. The reforming i.e. the conversion of hydrocarbons into H.sub.2, may be integrated in the fuel cell or connect to the latter.
DE 27 28 109 and GB 1,568,374 also disclose methods in which the H.sub.2 adsorbed on metals or metal compounds is released by heating. For this purpose, lithium borohydride is used in DE 27 28 109 and magnesium hydride is used in GB 1,568,374, the lithium borohydride and magnesium hydride being respectively charged with H.sub.2 in advance. This interesting form of H.sub.2 storage or H.sub.2 production consequently concerns the reversal of a physical effect which is bound to specific thermodynamic conditions.
For use with alkaline fuel cells, there has also been proposed (U.S. Pat. No. 3,511,710) a method in which the H.sub.2 contained in borohydride is oxidized at the anode directly with O.sub.2 to give water.
Under certain conditions, such as for example by the use of water solution containing sodium chloride (for example sea water; CA 2,079,925), magnesium can be chemically converted with water to give magnesium hydroxide, with the release of H.sub.2. However, this conversion requires the presence of catalysts such as cobalt, zinc etc. and, in particular, chlorine, which neutralizes the internal electric voltages which build up in the material during the reaction with water.
For the operation of relatively small fuel cells, used for example in the leisure sector on camping sites, in caravans or on sailing boats, in the training sector for demonstration purposes, in the military sector or on expeditions, the previously mentioned possibilities for producing or supplying H.sub.2 are not practicable.
EP 0 813 264 discloses a portable fuel cell arrangement for the conversion of liquid or gaseous hydrocarbons into electric DC current. Fuel cells of the solid-polymer type and a sealing container in which hydrogen gas for supplying the fuel cells is released from chemical compounds are disclosed. A hydrogen line, into which a valve or a hydrogen-flow and/or hydrogen-pressure control are fitted, connects the container to the fuel cells in a removable manner.
WO 98/35398 likewise discloses a portable fuel cell arrangement for the conversion of liquid or gaseous hydrocarbons into electric DC current. This fuel cell arrangement comprises disc-shaped, preferably circular, fuel cells for axial arrangement in layers in a stack, which is fixed by a tension rod. The fuel cell has for receiving the tension rod and for letting in a first gas a preferably central opening and is characterized by a special form of the gas line which permits a uniform distribution of the reaction at the anode and consequently a uniform current distribution in the plane of a fuel cell or a high average power per unit area. However, no solution for producing a fuel gas is proposed here.